JP2018054875A - Optical scanner, image formation apparatus and reflection surface identification method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical scanner, image formation apparatus and reflection surface identification method which can suppress reduction in the identification accuracy of a reflection surface of a rotary polygon mirror.SOLUTION: An image formation apparatus includes: a drive motor which rotates a polygon mirror; and an optical detection unit which detects light scanned by the polygon mirror at a prescribed detection position within an optical scan region by the polygon mirror. The image formation apparatus acquires an interval between the detection timing of light by the optical detection unit corresponding to a reference reflection surface of the polygon mirror and the output timing of a drive signal input to the drive motor first after the detection timing on the basis of the detection result of the current flowing in the drive motor (steps S13, S14), measures the interval between the detection timing and the output timing in each detection cycle of the light by the optical detection unit (steps S15-S18), and identifies the reference reflection surface on the basis of the acquired acquisition interval and the measured measurement interval (step S19).SELECTED DRAWING: Figure 7

Description

  The present invention relates to an optical scanning device including a rotating polygon mirror, an image forming apparatus including the optical scanning device, and a reflecting surface identification method executed by the optical scanning device.

  An electrophotographic image forming apparatus includes a rotating polygon mirror that scans light emitted from a light source onto an image carrier such as a photosensitive drum. The rotary polygon mirror is rotationally driven by a drive motor such as a brushless motor. For example, the image forming apparatus includes a speed detection unit that outputs a detection signal having a frequency corresponding to the rotation speed of the drive motor based on an electrical signal output from each Hall element provided in the drive motor. In the image forming apparatus, the rotation speed of the drive motor is controlled by PLL (phase lock loop) control that supplies power corresponding to the phase difference between the detection signal and the drive signal of the drive motor to the drive motor.

  Further, in the image forming apparatus, the light emission timing corresponding to each line of the image data, that is, the electrostatic latent image is based on the light detection timing in the light detection unit capable of detecting the light of the light source scanned by the rotary polygon mirror. The image writing timing is determined. An image forming apparatus that can identify the reflecting surface of a rotating polygon mirror based on the light detection interval of the light detection unit is known (see, for example, Patent Document 1).

JP2013-1111796A

  By the way, it is conceivable to identify the reflecting surface of the rotary polygon mirror based on the interval between the light detection timing by the light detection unit and the output timing of the drive signal synchronized with the detection signal by the PLL control. Here, when the load of the drive motor increases due to deterioration of the drive motor or temperature change, the current flowing through the drive motor increases. In this case, the amplitude of the electric signal output from each of the Hall elements increases, and the output timing of the detection signal by the speed detector changes. Thereby, it is conceivable that the interval between the light detection timing by the light detection unit and the output timing of the drive signal is changed, and the identification accuracy of the reflecting surface of the rotary polygon mirror is lowered.

  An object of the present invention is to provide an optical scanning device, an image forming apparatus, and a reflecting surface identifying method capable of suppressing a reduction in the accuracy of identifying a reflecting surface of a rotary polygon mirror.

  An optical scanning device according to one aspect of the present invention includes a rotary polygon mirror, a drive motor, a speed detection unit, a drive control unit, a light detection unit, a detection processing unit, an acquisition processing unit, and a measurement processing unit. And an identification processing unit. The rotary polygon mirror has a plurality of reflection surfaces that reflect light emitted from a light source, and sequentially scans light on each of the reflection surfaces as it rotates. The drive motor rotates the rotary polygon mirror. The speed detection unit includes a Hall element that detects a rotational position of the drive motor, and the number of the reflective surfaces is larger than the number of the reflective surfaces during the rotation of the rotary polygon mirror. A detection signal is output. The drive control unit controls the drive of the drive motor and synchronizes the detection signal output from the speed detection unit with the drive signal of the drive motor. The light detection unit detects light scanned by the rotary polygon mirror at a predetermined detection position in a scanning region of light by the rotary polygon mirror. The detection processing unit detects a current flowing through the drive motor. The acquisition processing unit, based on the current detected by the detection processing unit, the light detection timing corresponding to a predetermined reference reflection surface among the plurality of reflection surfaces, and after the detection timing First, an interval from the output timing of the drive signal input to the drive control unit is acquired. The measurement processing unit measures an interval between the detection timing and the output timing for each light detection period by the light detection unit. The identification processing unit identifies the reference reflecting surface based on an acquisition interval acquired by the acquisition processing unit and a measurement interval measured by the measurement processing unit.

  An image forming apparatus according to another aspect of the present invention includes the optical scanning device.

  A reflecting surface identifying method according to another aspect of the present invention includes a rotating polygon mirror that includes a plurality of reflecting surfaces that reflect light emitted from a light source, and sequentially scans light on each of the reflecting surfaces with rotation, A drive motor for rotating the rotary polygon mirror; and a hall element for detecting a rotation position of the drive motor, and the number of the reflective surfaces is relatively larger than the number of the reflective surfaces during one rotation of the rotary polygon mirror. A speed detection unit that outputs a number of detection signals, a drive control unit that controls the drive of the drive motor and synchronizes the detection signal output from the speed detection unit with the drive signal of the drive motor; A detection step that is executed by an optical scanning device that includes a light detection unit that detects light scanned by the rotary polygon mirror at a predetermined detection position in a scanning region of light by the rotary polygon mirror. Measuring step, and an identification step. In the detection step, a current flowing through the drive motor is detected. In the acquisition step, based on the current detected in the detection step, the light detection timing corresponding to a predetermined reference reflection surface among the plurality of reflection surfaces and first after the detection timing. An interval from the output timing of the drive signal input to the drive control unit is acquired. In the measurement step, an interval between the detection timing and the output timing in each light detection period by the light detection unit is measured. In the identification step, the reference reflecting surface is identified based on the acquisition interval acquired in the acquisition step and the measurement interval measured in the measurement step.

  According to the present invention, an optical scanning device, an image forming apparatus, and a reflecting surface identifying method capable of suppressing a decrease in the accuracy of identifying a reflecting surface of a rotary polygon mirror are realized.

FIG. 1 is a diagram illustrating a configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a block diagram showing a system configuration of the image forming apparatus according to the embodiment of the present invention. FIG. 3 is a diagram illustrating a configuration of the optical scanning unit in the image forming apparatus according to the embodiment of the present invention. FIG. 4 is a block diagram showing the configuration of the optical scanning unit in the image forming apparatus according to the embodiment of the present invention. FIG. 5 is a timing chart showing the relationship between the input timing of the BD signal and the output timing of the drive signal in the image forming apparatus according to the embodiment of the present invention. FIG. 6 is an example of table data stored in the image forming apparatus according to the embodiment of the present invention. FIG. 7 is a flowchart illustrating an example of the reflection surface identification process executed by the image forming apparatus according to the embodiment of the present invention.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings for understanding of the present invention. The following embodiment is an example embodying the present invention, and does not limit the technical scope of the present invention.

[Schematic Configuration of Image Forming Apparatus 10]
First, a schematic configuration of an image forming apparatus 10 according to an embodiment of the present disclosure will be described with reference to FIGS. 1 and 2. Here, FIG. 1 is a schematic cross-sectional view showing the configuration of the image forming apparatus 10.

  The image forming apparatus 10 is a multifunction machine having a plurality of functions such as a facsimile function and a copy function, as well as a scan function for reading image data from a document and a print function for forming an image based on the image data. The present invention is applicable to image forming apparatuses such as printers, facsimile machines, and copiers.

  As shown in FIGS. 1 and 2, the image forming apparatus 10 includes an ADF 1, an image reading unit 2, an image forming unit 3, a paper feeding unit 4, a control unit 5, an operation display unit 6, and a storage unit 7.

  The ADF 1 is an automatic document conveyance device that includes a document setting unit, a plurality of conveyance rollers, a document pressing unit, and a paper discharge unit, and conveys a document read by the image reading unit 2. The image reading unit 2 includes a document table, a light source, a plurality of mirrors, an optical lens, and a CCD (Charge Coupled Device), and can read image data from the document.

  The image forming unit 3 is an image forming process (printing process) that forms an image by an electrophotographic method based on image data read by the image reading unit 2 or image data input from an information processing apparatus such as an external personal computer. ) Can be executed. Specifically, as shown in FIG. 1, the image forming unit 3 includes a photosensitive drum 31 (an example of an image carrier in the present invention), a charger 32, an optical scanning unit 33, a developing unit 34, a transfer roller 35, A cleaning device 36, a fixing roller 37, a pressure roller 38, and a paper discharge tray 39 are provided.

  The paper feed unit 4 includes a paper feed cassette and a plurality of transport rollers, and supplies sheets stored in the paper feed cassette to the image forming unit 3. The sheets stored in the paper feed cassette are sheet materials such as paper, coated paper, postcards, envelopes, and OHP sheets.

  In the image forming unit 3, an image is formed on the sheet supplied from the paper feeding unit 4 according to the following procedure, and the sheet after the image formation is discharged to the paper discharge tray 39.

  First, the surface of the photosensitive drum 31 is uniformly charged to a predetermined potential by the charger 32. Next, the light scanning unit 33 irradiates the surface of the photosensitive drum 31 with light based on the image data. Thereby, an electrostatic latent image corresponding to the image data is formed on the surface of the photosensitive drum 31. The electrostatic latent image on the photosensitive drum 31 is developed (visualized) as a toner image by the developing device 34. The developing device 34 is supplied with toner (developer) from a toner container 34 </ b> A that can be attached to and detached from the image forming unit 3.

  Subsequently, the toner image formed on the photosensitive drum 31 is transferred onto the sheet by the transfer roller 35. Thereafter, the toner image transferred to the sheet is heated and fixed by the fixing roller 37 when the sheet passes between the fixing roller 37 and the pressure roller 38. The toner remaining on the surface of the photosensitive drum 31 is removed by the cleaning device 36.

  The control unit 5 includes control devices such as a CPU, ROM, RAM, and EEPROM (registered trademark) (not shown). The CPU is a processor that executes various arithmetic processes. The ROM is a non-volatile storage unit in which information such as a control program for causing the CPU to execute various processes is stored in advance. The RAM is a volatile storage unit used as a temporary storage memory (working area) for various processes executed by the CPU. The EEPROM is a nonvolatile storage unit. In the control unit 5, various control programs stored in advance in the ROM are executed by the CPU. As a result, the image forming apparatus 10 is comprehensively controlled by the control unit 5. The control unit 5 may be an electronic circuit such as an integrated circuit (ASIC), and is a control unit provided separately from the main control unit that controls the image forming apparatus 10 in an integrated manner. May be.

  The operation display unit 6 is a display unit such as a liquid crystal display that displays various types of information in response to control instructions from the control unit 5, and an operation key or touch panel that inputs various types of information to the control unit 5 in response to user operations. And so on.

  The storage unit 7 is a non-volatile storage device such as a flash memory. The storage unit 7 may be the ROM of the control unit 5 or the EEPROM.

[Configuration of Optical Scanning Unit 33]
Next, the optical scanning unit 33 will be described with reference to FIGS. Here, FIG. 3 is a perspective view showing a configuration of the optical scanning unit 33. FIG. 4 is a block diagram showing the speed detector 334 and its peripheral configuration. 5 shows the input timing of the light reception signal (hereinafter referred to as “BD signal”) X1 output from the light detection unit 338 to the control unit 5 and the control unit of the drive signal X2 input to the drive control unit 335. 5 is a timing chart showing the relationship with the output timing from FIG.

  In FIG. 5, the input timing of the BD signal X1 is represented by a falling edge of the electric signal (voltage). In FIG. 5, the output timing of the drive signal X2 is represented by the falling edge of the electrical signal (voltage).

  The light scanning unit 33 scans light corresponding to the image data on the photosensitive drum 31 to form an electrostatic latent image corresponding to the image data on the photosensitive drum 31.

  Specifically, as shown in FIGS. 2 and 3, the optical scanning unit 33 includes a light source 331, a polygon mirror 332, a drive motor 333, a speed detection unit 334, a drive control unit 335, a current detection unit 336, and an fθ lens 337A. , An fθ lens 337B, a total reflection mirror 337C, a light detection unit 338, a housing 330 that accommodates these components, and an exit port 330A formed in the housing 330. In the image forming unit 3, the optical scanning unit 33 is disposed above the photosensitive drum 31 and at a position where the longitudinal direction of the ejection port 330 </ b> A and the axial direction of the photosensitive drum 31 are parallel.

  The light source 331 emits light corresponding to the image data. For example, the light source 331 is a laser diode.

  The polygon mirror 332 scans the photosensitive drum 31 with light emitted from the light source 331. For example, the polygon mirror 332 is formed in a regular pentagonal plan view as shown in FIG. 3, and has reflection surfaces 332 </ b> A to 332 </ b> E that reflect light emitted from the light source 331. Note that the number of reflection surfaces of the polygon mirror 332 may be other than five.

  The polygon mirror 332 rotates in the rotation direction D1 shown in FIG. 3 by the rotational driving force supplied from the drive motor 333. Thereby, the polygon mirror 332 sequentially scans the light on each of the reflection surfaces 332A to 332E as it rotates. Here, the polygon mirror 332 is an example of a rotating polygon mirror in the present invention.

  The drive motor 333 supplies rotational driving force to the polygon mirror 332 to rotate the polygon mirror 332. For example, the drive motor 333 is a brushless motor.

  The speed detection unit 334 outputs a detection signal X3 (see FIG. 4) having a frequency corresponding to the rotational speed of the drive motor 333. Specifically, the speed detection unit 334 outputs detection signals X3 having a number that is greater than the number of reflection surfaces of the polygon mirror 332 and that is relatively prime to the number of reflection surfaces of the polygon mirror 332 while the polygon mirror 332 rotates once. Output. As illustrated in FIG. 4, the speed detection unit 334 includes Hall elements 334 </ b> A to 334 </ b> F disposed in the drive motor 333 and a signal processing circuit 334 </ b> G.

  Hall elements 334 </ b> A to 334 </ b> F detect the rotational position of drive motor 333. For example, the Hall elements 334A to 334F are arranged at intervals of 60 degrees around the rotor in the drive motor 333 along the rotation direction of the rotor. Each of the Hall elements 334A to 334F outputs an electric signal corresponding to the strength of the magnetic field at the arrangement position that changes according to the rotation of the rotor. The electrical signal output from each of the hall elements 334A to 334F is output to the signal processing circuit 334G.

  The signal processing circuit 334G outputs the detection signal X3 based on the electrical signal output from each of the Hall elements 334A to 334F. For example, the signal processing circuit 334G outputs the detection signal X3 every time an electrical signal output from any of the Hall elements 334A to 334F exceeds a predetermined threshold. For example, the signal processing circuit 334G outputs detection signals X3 as many as the number of Hall elements 334A to 334F while the polygon mirror 332 rotates once. The detection signal X3 output from the signal processing circuit 334G is input to the drive control unit 335.

  The drive control unit 335 rotates the drive motor 333 at a speed corresponding to the frequency of the drive signal X2 (see FIG. 4) input from the control unit 5. Specifically, the drive control unit 335 rotates the drive motor 333 at a speed corresponding to the frequency of the drive signal X2 by feedback control based on the detection signal X3 output from the signal processing circuit 334G.

  More specifically, the drive control unit 335 performs PLL (phase lock loop) control that supplies power corresponding to the phase difference between the detection signal X3 and the drive signal X2 to the drive motor 333. As a result, the detection signal X3 is synchronized with the drive signal X2 (see FIG. 5), and the drive motor 333 is rotated at a speed corresponding to the frequency of the drive signal X2.

  The current detection unit 336 detects the current flowing through the drive motor 333. For example, the current detection unit 336 detects a current flowing on the power supply path by detecting a voltage drop in a shunt resistor provided on the power supply path connecting the drive motor 333 and the drive control unit 335. The current detection unit 336 inputs an electric signal X4 (see FIG. 4) indicating the current value of the detected current to the control unit 5.

  The fθ lens 337A and the fθ lens 337B convert light scanned at a constant angular speed by the polygon mirror 332 into light scanned at a constant speed along the scanning direction D2 (see FIG. 3). The total reflection mirror 337C reflects the light that has passed through the fθ lens 337B toward the surface of the photosensitive drum 31. The emission port 330A has a long opening through which light reflected by the total reflection mirror 337C is emitted toward the surface of the photosensitive drum 31, and a transparent glass plate or acrylic plate that closes the opening.

  The light detection unit 338 detects light scanned by the polygon mirror 332 at a predetermined detection position in the light scanning region by the polygon mirror 332. For example, the light detection unit 338 is an optical sensor having a light receiving unit. For example, the detection position is a position outside the scanning region that is upstream of the scanning direction D2 and is not reflected by the total reflection mirror 337C. The light detection unit 338 outputs a BD signal X1 (see FIG. 4) in response to detection of light scanned by the polygon mirror 332.

  The BD signal X1 output from the light detection unit 338 is input to the control unit 5. Based on the input timing of the BD signal X1, the control unit 5 determines the light emission start timing corresponding to one line of the image data from the light source 331, that is, the electrostatic latent image writing timing in the scanning direction D2.

  Here, in the image forming apparatus 10, as described above, while the polygon mirror 332 is rotated once by the speed detection unit 334, the number of the reflection surfaces of the polygon mirror 332 is larger than the number of the reflection surfaces of the polygon mirror 332. As many detection signals X3 as are output. Therefore, as shown in FIG. 5, within the light detection period (input period of the BD signal X1 to the control unit 5) T2 by the light detection unit 338, the drive signal X2 synchronized with the detection signal X3 is at least once. Output from the control unit 5. Further, in the image forming apparatus 10, as shown in FIG. 5, light detection timing (BD signal X <b> 1 to the control unit 5) is detected by the light detection unit 338 in each detection cycle T <b> 2 within the rotation cycle T <b> 1 of the polygon mirror 332. And the output timing of the drive signal X2 first input to the drive control unit 335 after the detection timing (t21 to t25) are different.

  By the way, it is considered that the reflecting surfaces 332A to 332E of the polygon mirror 332 are identified based on the interval between the light detection timing by the light detection unit 338 and the output timing of the drive signal X2 synchronized with the detection signal X3 by the PLL control. It is done. Here, when the load of the drive motor 333 increases due to deterioration of the drive motor 333 or temperature change, the current flowing through the drive motor 333 increases. In this case, the amplitude of the electrical signal output from each of the Hall elements 334A to 334F increases, and the output timing of the detection signal X3 by the speed detection unit 334 changes. As a result, the interval between the light detection timing by the light detection unit 338 and the output timing of the drive signal X2 is changed, and the identification accuracy of the reflection surfaces 332A to 332E of the polygon mirror 332 may be lowered.

  On the other hand, in the image forming apparatus 10 according to the embodiment of the present invention, it is possible to suppress a decrease in the identification accuracy of the reflection surfaces 332A to 332E of the polygon mirror 332 as described below.

  Specifically, the ROM of the control unit 5 stores in advance a reflection surface identification program for causing the CPU to execute a reflection surface identification process described later (see the flowchart of FIG. 7). The reflection surface identification program is recorded on a computer-readable recording medium such as a CD, DVD, or flash memory, and is read from the recording medium and installed in a storage unit such as the EEPROM of the control unit 5. It may be a thing.

  And the control part 5 contains the detection process part 51, the acquisition process part 52, the measurement process part 53, the identification process part 54, and the width correction part 55, as FIG. 2 shows. Specifically, the control unit 5 executes the reflection surface identification program stored in the ROM using the CPU. Accordingly, the control unit 5 functions as a detection processing unit 51, an acquisition processing unit 52, a measurement processing unit 53, an identification processing unit 54, and a width correction unit 55. Here, the device including the optical scanning unit 33 and the control unit 5 is an example of the optical scanning device in the present invention.

  The detection processing unit 51 detects a current flowing through the drive motor 333.

  Specifically, the detection processing unit 51 detects the current flowing through the drive motor 333 based on the electrical signal X4 output from the current detection unit 336.

  Based on the current detected by the detection processing unit 51, the acquisition processing unit 52 detects light by the light detection unit 338 corresponding to a predetermined reference reflection surface among the reflection surfaces 332A to 332E of the polygon mirror 332. And the output timing of the drive signal X2 input to the drive controller 335 first after the detection timing.

  For example, in the image forming apparatus 10, the light detection timing of the light detection unit 338 on the reference reflection surface and the drive signal that is input first to the drive control unit 335 after the detection timing, corresponding to each current flowing in the drive motor 333. Table data D10 (see FIG. 6) indicating an interval from the output timing of X2 is stored in the storage unit 7 in advance. For example, the table data D10 is acquired when the image forming apparatus 10 is manufactured. Specifically, the load of the drive motor 333 is changed to various values, and for each current flowing through the drive motor 333 corresponding to the load, after the detection timing of the light by the light detection unit 338 on the reference reflection surface and after the detection timing First, it is acquired by measuring an interval from the output timing of the drive signal X2 input to the drive control unit 335.

  For example, the acquisition processing unit 52 detects the light detection timing and the detection by the light detection unit 338 on the reference reflection surface corresponding to the current detected by the detection processing unit 51 based on the table data D10 read from the storage unit 7. An interval from the output timing of the drive signal X2 input to the drive control unit 335 first after the timing is acquired.

  The measurement processing unit 53 includes the detection timing of the light by the light detection unit 338 at each light detection period T2 by the light detection unit 338, and the output timing of the drive signal X2 input to the drive control unit 335 first after the detection timing. Measure the interval.

  For example, the measurement processing unit 53 causes the light source 331 to emit light at a predetermined timing and inputs the drive signal X2 to the drive control unit 335 to rotate the drive motor 333 at a predetermined reference speed. Let And the measurement process part 53 measures the space | interval with the output timing of the drive signal X2 input into the drive control part 335 first after the said detection timing and the said detection timing for every detection period T2. The predetermined timing is when the power of the image forming apparatus 10 is turned on, when returning from a sleep state in which some functions of the image forming apparatus 10 are stopped, and when the printing process is executed. is there.

  The identification processing unit 54 identifies the reference reflecting surface based on the acquisition interval acquired by the acquisition processing unit 52 and the measurement interval measured by the measurement processing unit 53.

  For example, when the difference between the acquisition interval and the measurement interval is less than a preset allowable value, the identification processing unit 54 reflects light emitted from the light source 331 in the detection cycle T2 corresponding to the measurement interval. The reflecting surface to be determined is the reference reflecting surface.

  The width correction unit 55 corrects the width of one pixel of the electrostatic latent image formed on the photosensitive drum 31 by each of the reflection surfaces 332A to 332E of the polygon mirror 332 based on the identification result by the identification processing unit 54.

  For example, in the image forming apparatus 10, the irradiation time of light to the photosensitive drum 31 corresponding to each of the reflection surfaces 332 </ b> A to 332 </ b> E is stored in the storage unit 7 in advance. For example, the irradiation time corresponding to each of the reflection surfaces 332 </ b> A to 332 </ b> E is measured using a jig or the like in advance by a manufacturer of the image forming apparatus 10 and stored in a predetermined storage area of the storage unit 7. Is done. For example, the width correction unit 55 corrects each line of image data corresponding to each of the reflection surfaces 332A to 332E based on the irradiation time corresponding to each of the reflection surfaces 332A to 332E read from the storage unit 7, thereby reflecting The width of one pixel of the electrostatic latent image formed on the photosensitive drum 31 by each of the surfaces 332A to 332E is corrected.

[Reflecting surface identification processing]
Hereinafter, an example of the procedure of the reflection surface identification process executed by the control unit 5 in the image forming apparatus 10 will be described with reference to FIG. Here, steps S11, S12,... Represent the numbers of processing procedures (steps) executed by the control unit 5.

<Step S11>
First, in step S11, the control unit 5 determines whether or not the timing has arrived.

  Here, if the control part 5 judges that the said timing has come (Yes side of S11), it will transfer a process to step S12. If the timing has not arrived (No side of S11), the control unit 5 waits for the arrival of the timing in step S11.

<Step S12>
In step S12, the control unit 5 causes the light source 331 to emit light and inputs the drive signal X2 to the drive control unit 335 to rotate the drive motor 333 at the reference speed.

<Step S13>
In step S <b> 13, the control unit 5 detects the current flowing through the drive motor 333. Here, the process of step S13 is an example of the detection step in the present invention, and is executed by the detection processing unit 51 of the control unit 5.

  Specifically, the control unit 5 detects the current flowing through the drive motor 333 based on the electrical signal X4 output from the current detection unit 336.

<Step S14>
In step S14, the control unit 5 is first input to the drive control unit 335 after the detection timing of the light by the light detection unit 338 corresponding to the reference reflection surface and the detection timing based on the current detected in step S13. The interval with the output timing of the drive signal X2 is acquired. Here, the process of step S14 is an example of an acquisition step in the present invention, and is executed by the acquisition processing unit 52 of the control unit 5.

  For example, based on the table data D10 read from the storage unit 7, the control unit 5 first detects light detection timing by the light detection unit 338 on the reference reflecting surface corresponding to the current detected in step S13, and first after the detection timing. The interval from the output timing of the drive signal X2 input to the drive control unit 335 is acquired.

<Step S15>
In step S <b> 15, the control unit 5 determines whether or not the BD signal X <b> 1 is input from the light detection unit 338.

  When the control unit 5 determines that the BD signal X1 is input from the light detection unit 338 (Yes in S15), the control unit 5 shifts the process to step S16. If the BD signal X1 is not input from the light detection unit 338 (No in S15), the control unit 5 waits for the input of the BD signal X1 from the light detection unit 338 in step S15.

<Step S16>
In step S <b> 16, the control unit 5 outputs the detection timing of the light by the light detection unit 338 (when the BD signal X <b> 1 is input in step S <b> 15) and the drive signal X <b> 2 that is first input to the drive control unit 335 after the detection timing. Start measuring the interval with the timing.

<Step S17>
In step S17, the control unit 5 determines whether or not the drive signal X2 is output.

  Here, if the control part 5 judges that the drive signal X2 was output (Yes side of S17), it will transfer a process to step S18. If the drive signal X2 is not output (No side of S17), the control unit 5 waits for the output of the drive signal X2 in step S17.

<Step S18>
In step S18, the control unit 5 ends the measurement started in step S16. Here, steps S11, S12, and steps S15 to S18 are examples of measurement steps in the present invention, and are executed by the measurement processing unit 53 of the control unit 5.

<Step S19>
In step S19, the control unit 5 identifies the reference reflecting surface based on the acquisition interval acquired in step S14 and the measurement interval measured in step S18. Here, the process of step S19 is an example of the identification step in the present invention, and is executed by the identification processing unit 54 of the control unit 5.

  For example, when the difference between the acquisition interval and the measurement interval is less than the allowable value, the control unit 5 has a reflecting surface that reflects the light emitted from the light source 331 in the detection cycle T2 corresponding to the measurement interval. The reference reflection surface is determined.

<Step S20>
In step S20, the control unit 5 determines whether or not the reference reflecting surface has been identified in step S19.

  Here, if the control part 5 judges that the said reference reflective surface was able to be identified (Yes side of S20), it will transfer a process to step S21. If the reference reflecting surface cannot be identified (No side in S20), the control unit 5 moves the process to step S15. And the control part 5 performs the process of step S15-step S19 until it can identify the said reference | standard reflective surface by step S19.

<Step S21>
In step S21, the control unit 5 corrects the width of one pixel of the electrostatic latent image formed on the photosensitive drum 31 by each of the reflection surfaces 332A to 332E based on the identification result in step S19. Here, the process of step S <b> 21 is executed by the width correction unit 55 of the control unit 5.

  For example, the control unit 5 corrects each line of the image data corresponding to each of the reflection surfaces 332A to 332E based on the irradiation time corresponding to each of the reflection surfaces 332A to 332E read from the storage unit 7, thereby reflecting the reflection surface. The width of one pixel of the electrostatic latent image formed on the photosensitive drum 31 is corrected by each of 332A to 332E. As a result, variations in the same magnification in the main scanning direction in the printed image due to the surface tilt of the reflecting surfaces 332A to 332E of the polygon mirror 332 are corrected.

  As described above, in the image forming apparatus 10, based on the detection result of the current flowing through the drive motor 333, the light detection unit 338 corresponding to the reference reflection surface and the drive control unit 335 first after the detection timing. An interval from the output timing of the drive signal X2 input to the signal is acquired. As a result, the current flowing through the drive motor 333 increases due to deterioration of the drive motor 333 or a temperature change, and the interval between the light detection timing by the light detection unit 338 and the output timing of the drive signal X2 changes. In addition, the reference reflecting surface can be identified based on the interval after the change. Accordingly, it is possible to suppress a decrease in the identification accuracy of the reflection surfaces 332A to 332E of the polygon mirror 332.

1 ADF
2 Image reading unit 3 Image forming unit 4 Paper feeding unit 5 Control unit 6 Operation display unit 7 Storage unit 10 Image forming apparatus 33 Optical scanning unit 51 Detection processing unit 52 Acquisition processing unit 53 Measurement processing unit 54 Identification processing unit 55 Width correction unit 331 Light source 332 Polygon mirror 333 Drive motor 334 Speed detector 335 Drive controller 336 Current detector 338 Light detector

Claims (5)

A rotating polygon mirror that has a plurality of reflecting surfaces that reflect light emitted from the light source, and sequentially scans the light on each of the reflecting surfaces with rotation;
A drive motor for rotating the rotary polygon mirror;
A speed at which a Hall element that detects the rotational position of the drive motor is provided, and the number of detection signals that are larger than the number of the reflective surfaces and relatively prime to the number of the reflective surfaces is output during one rotation of the rotary polygon mirror. A detection unit;
A drive control unit that controls driving of the drive motor and synchronizes the detection signal output from the speed detection unit with the drive signal of the drive motor;
A light detection unit for detecting light scanned by the rotary polygon mirror at a predetermined detection position in a scanning region of light by the rotary polygon mirror;
A detection processing unit for detecting a current flowing in the drive motor;
Based on the current detected by the detection processing unit, the light detection unit corresponding to a predetermined reference reflection surface among the plurality of reflection surfaces, and the drive control unit first after the detection timing. An acquisition processing unit for acquiring an interval from the output timing of the drive signal input to
A measurement processing unit for measuring an interval between the detection timing and the output timing in each light detection period by the light detection unit;
An identification processing unit for identifying the reference reflecting surface based on an acquisition interval acquired by the acquisition processing unit and a measurement interval measured by the measurement processing unit;
An optical scanning device comprising: The drive control unit synchronizes the detection signal with the drive signal by PLL control that supplies power corresponding to the phase difference between the detection signal and the drive signal to the drive motor.
The optical scanning device according to claim 1. A width correction unit that corrects the width of one pixel of the electrostatic latent image formed on the image carrier by each of the reflection surfaces based on the identification result by the identification processing unit;
The optical scanning device according to claim 1.   An image forming apparatus comprising the optical scanning device according to claim 1. A plurality of reflecting surfaces for reflecting light emitted from the light source, a rotating polygon mirror that sequentially scans the light with each reflecting surface as it rotates, a driving motor that rotates the rotating polygon mirror, and A speed detector that includes a Hall element that detects a rotational position, and outputs a number of detection signals that are relatively prime to the number of the reflecting surfaces, more than the number of the reflecting surfaces, while the rotating polygonal mirror makes one rotation; A drive control unit for controlling the drive of the drive motor to synchronize the detection signal output from the speed detection unit with the drive signal of the drive motor; and a predetermined in a scanning region of light by the rotary polygon mirror A light detection unit that detects light scanned by the rotary polygon mirror at a detection position, and a reflection surface identification method executed by an optical scanning device comprising:
A detection step of detecting a current flowing through the drive motor;
Based on the current detected by the detection step, the light detection unit corresponding to a predetermined reference reflection surface among the plurality of reflection surfaces and the drive control unit first after the detection timing. An acquisition step of acquiring an interval with an output timing of the input drive signal;
A measurement step of measuring an interval between the detection timing and the output timing in each light detection period by the light detection unit;
An identification step for identifying the reference reflecting surface based on the acquisition interval acquired by the acquisition step and the measurement interval measured by the measurement step;
Reflective surface identification method including:

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